From d5dd90881087d6e6940f60a62e1d708670379ff1 Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Wed, 23 Mar 2005 20:34:39 +0000
Subject: *** empty log message ***

---
 .../scala/tools/nsc/typechecker/EtaExpansion.scala | 70 ++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 sources/scala/tools/nsc/typechecker/EtaExpansion.scala

(limited to 'sources/scala/tools/nsc/typechecker/EtaExpansion.scala')

diff --git a/sources/scala/tools/nsc/typechecker/EtaExpansion.scala b/sources/scala/tools/nsc/typechecker/EtaExpansion.scala
new file mode 100644
index 0000000000..4c8052563c
--- /dev/null
+++ b/sources/scala/tools/nsc/typechecker/EtaExpansion.scala
@@ -0,0 +1,70 @@
+/* NSC -- new scala compiler
+ * Copyright 2005 LAMP/EPFL
+ * @author  Martin Odersky
+ */
+// $Id$
+package scala.tools.nsc.typechecker;
+
+import collection.mutable.ListBuffer;
+import symtab.Flags._;
+
+class EtaExpansion: Analyzer {
+
+  import global._;
+  import posAssigner.atPos;
+
+  /** Expand partial function applications of type `type'.
+   *
+   *  p.f(es_1)...(es_n)
+   *     ==>  {
+   *            private synthetic val eta$f    = p.f   // if p is not stable
+   *            ...
+   *            private synthetic val eta$e_i = e_i    // if e_i is not stable
+   *             ...
+   *
+   *            (ps_1 => ... => ps_m => eta$f([es_1])...([es_m])(ps_1)...(ps_m))
+   *          }
+   *  tree is already attributed
+   */
+  def etaExpand(tree: Tree, tpe: Type): Tree = {
+    var cnt = 0;
+    def freshName() = { cnt = cnt + 1; newTermName("eta$" + cnt) }
+    val defs = new ListBuffer[Tree];
+
+    /** Append to `defs' value definitions for all non-stable subexpressions
+     *  of the function application `tree' */
+    def liftoutPrefix(tree: Tree): Tree = {
+      def liftout(tree: Tree): Tree =
+	if (treeInfo.isPureExpr(tree)) tree
+	else {
+	  val vname: Name = freshName();
+	  defs += ValDef(SYNTHETIC, vname, TypeTree(), tree);
+	  Ident(vname)
+	}
+      tree match {
+	case Apply(fn, args) =>
+          copy.Apply(tree, liftoutPrefix(fn), args mapConserve liftout);
+	case TypeApply(fn, args) =>
+          copy.TypeApply(tree, liftoutPrefix(fn), args)
+	case Select(qual, name) =>
+          copy.Select(tree, liftout(qual), name)
+        case Ident(name) =>
+          tree
+      }
+    }
+
+    /** Eta-expand lifted tree */
+    def expand(tree: Tree, tpe: Type): Tree = tpe match {
+      case MethodType(formals, restpe) =>
+        val params = formals map (formal =>
+          ValDef(SYNTHETIC | PARAM, freshName(), TypeTree().setType(formal), EmptyTree));
+        val args = params map (param => Ident(param.name));
+        Function(params, expand(Apply(tree, args), restpe))
+      case _ =>
+        tree
+    }
+
+    val tree1 = liftoutPrefix(tree);
+    atPos(tree.pos)(Block(defs.toList, expand(tree1, tpe)))
+  }
+}
-- 
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